Preparation of novel homo- and copolymers using atom transfer radical polymerization

ABSTRACT

The present invention is directed to a process of atom (or group) transfer radical polymerization for the synthesis of novel homopolymer or a block or graft copolymer, optionally containing at least one polar group, with well defined molecular architecture and narrow polydispersity index, in the presence of an initiating system comprising (i) an initiator having a radically transferrable atom or group, (ii) a transition metal compound, and (iii) a ligand; the present invention is also directed to the synthesis of a macromolecule having at least two halogen groups which can be used as a macroinitiator component (i) to subsequently form a block or graft copolymer by an atom or group transfer radical polymerization process; the present invention is also directed to a process of atom or group transfer radical polymerization for the synthesis of a branched or hyperbranched polymer; in addition, the present invention is directed to a process of atom or group transfer radical polymerization for the synthesis of a macroinitiator which can subsequently be used to produce a block or graft copolymer.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

This invention relates to a novel method for preparing new homo- andco-polymers by Atom Transfer Radical Polymerization and novelcompositions of homo- and copolymers thereof exhibiting narrowpolydispersity index.

2. Description of the Related Art:

The formation of block or graft copolymers of non-vinyl polymers withvinyl monomers by a radical mechanism, has been reported to have beenachieved by two methods. One is the use of an end functional polymerwhich can react with an end or pendent groups of the second polymer; thesecond method is to use a starting step-grown polymer as amacroinitiator and grow the vinyl polymer from it, or the use of amonofunctional vinyl polymer in a step growth polymerization with AA andBB monomers.

However, both of the above methods have certain limitations. The firstmethod requires that well defined vinyl polymers with knownfunctionalities be made. The other method requires that functionalgroups must be present at the ends of the polymer (block) or dispersedalong the polymer backbone (graft) which can react with those on thevinyl polymer. Also, if the vinyl polymer is not compatible with thegrowing polycondensation polymer the polymerization will result inincomplete formation of a block or graft copolymer and a mixture ofhomopolymers. In the second method, by using conventional radicalpolymerization, the generation of a radical at either a pendent group orat a chain end results not only in the synthesis of homopolymer, due totransfer to monomer or polymer, but also may lead to the formation ofcrosslinked gels.

Thus, a polymerization can be initiated by decomposition of a functionalgroup (azo, peroxy, etc.) either in the macroinitiator's backbone oralong a pendent side group, Scheme 1. Further, an irreversibleactivation of a functional group can take place at the polymer chainends or attached to a pendent side group, Scheme 2. ##STR1##

The decomposition of functional groups in a macroinitiator backbone isaccomplished by copolymerization of a functional monomer during thesynthesis of the macroinitiator. The functional monomer contains afunctional group which can decompose. These radicals can then initiatethe polymerization of a vinyl monomer to form a block copolymer. If morethan one functional group is present in the macroinitiator, then thechain can be broken into smaller chains which have radicals at bothends.

In the literature, there are some examples of the incorporation of azogroups in the backbone of polymer chains. Akar et al (Polym. Bull. 1986,15, 293) and Hizal et al (Polymer, 1989, 30,722) use a difunctionalcationic initiator with a central azo group. After the synthesis of apolymer by cationic polymerization, the azo group can be decomposed toform polymer chains with a radical at one end capable of initiatingradical polymerization. This results in the formation of AB blockcopolymers.

Udea et al (Kobunshi Ronbunshu, 1990, 47,321) discusses the use ofazodiols, as comonomers, in condensation polymerizations allowing forthe introduction of more than one azo group per polymer chain.Decomposition of this macroinitiator in the presence of vinyl monomerresults in the formation of AB block copolymers.

Azodiamines have reportedly been used (Vaslov et al, Makromol. Chemie1982, 183,2635) as a comonomer in the ring-opening polymerization ofN-carboxy anhydrides in the synthesis of polypeptides. Again, thesepolymers are macroinitiators which can form ABA triblocks bydecomposition, followed by initiation of a radical polymerization.

ABA block copolymers have also been synthesized by macroinitiators whichhave azo groups at the ends of the polymer chain. These macroinitiatorswere synthesized by the reaction of an azo compound, which had an acidchloride functional group, with the diol end groups of poly(ethyleneoxide) (PEO) or poly(dimethylsiloxane) (PDMS)(Harabaglu, Makromol. Chem.Rapid Commun. 1990, 11,433). Decomposition of the azo end groupsresulted in either a PEO or PDMS macro radical. When this was done inthe presence of a vinyl monomer, ABA polymers were synthesized. However,a radical complementary to the macroradical was also generated resultingin the formation of homopolymer.

Macroinitiators with side chain azo groups (Kerber et al., Makromol.Chem. 1979, 180,609; Nuyken et al., Polym., Bull 1989, 21,23) orperoxyester (Neckers, J. Radiat. Curing 1983, 10,19; Gupta, J. Polym.Sci., Polym. Chem. Ed. 1982, 20, 147) groups were used in the synthesisof graft copolymers. These macroinitiators were synthesized by the useof comonomers in step-growth polymers. These systems also formedhomopolymer upon decomposition of the peroxyester.

Another category of macroinitiators are those which possess a functionalgroup that can be activated to form a radical. One such example isreported by Bamford (Bamford, New Trends in the Photochemistry ofPolymers; Elsevier Applied Science Publishers, London, 1985) whentrichloro polymer end groups were irradiated in the presence ofmanganese pentacarbonyl. In the presence of a monomer, block copolymerswere formed.

Polystyrene with dimethylamino end groups, when irradiated in thepresence of 9-fluorenone and a monomer, gave block copolymers (Yagci,Polymer Commun; 1990, 31,7). This was done by formation of a radicalthrough the reaction of the dimethyl amine and the triplet state of thearomatic ketone. By analogy, graft copolymers were synthesized by usingpoly(styrene-co-p-N,N'-dimethylamino styrene) as the macroinitiator(Kinstle et al., J. Radiat. Curing 1975, 2,7).

Although these methods have produced block and graft copolymers, thematerials that have been prepared are not well defined. In most cases,homopolymers of the vinyl monomers are formed due to transfer to monomerduring the radical polymerization or because of a second radical formedduring the decomposition of the azo or peroxy group, Scheme 1. In thesynthesis of graft copolymers, crosslinked gels can be formed iftermination of the growing vinyl polymer is by combination. Themolecular weights of the grafts or blocks that are synthesized by theradical polymerizations are not well defined. Also, not all of the azo(or peroxy) groups may decompose and/or initiate polymerization duringthe synthesis of a block or graft copolymer. Because of incompleteinitiation, the number of grafts, or length of blocks cannot beaccurately predicted.

Thus, there is a need for a method to prepare block and graft copolymersthat are well defined and free of homopolymer.

Further, Flory (Flory, P. J. J. Am. Chem. Soc., 1952, 74,2718) firsttheorized that the copolymerization of a difunctional monomer with AB₂(see definition below) monomers would lead to branched structures. Inhis proposal, the density of branching could be controlled by varyingthe relative concentration of AB₂ monomer to difunctional monomer. Thisproposal was first put to use in the step-growth synthesis ofpolyphenylenes by Kim and Webster. (Webster, O. W.; Kim, Y. H. J. Am.Chem. Soc., 1990 112,4592; Webster, O. W., Kim, Y. H., Macromolecules1992, 25,5561). Subsequently, it was extended to other step-growthpolymerizations such as aromatic (Frechet, J. M. J.; Hawker, C. J.; Lee,R. J. Am. Chem. Soc. 1991, 113,4583.) and aliphatic (Hult, A.;Malmstrom, E.; Johansson, M. J. Polym. Sci. Polym. Chem. Ed. 1993,31,619) esters, siloxanes (Mathias, L. J.; Carothers, T. W. J. Am. Chem.Soc. 1991, 113,4043) and amines (Suzuki, M.; Li, A.; Saegusa, T.Macromolecules 1992, 25,7071). Later, it was extended to cationic chaingrowth polymerizations by Frechet et al., (Frechet, J. M. J.; Henmi, M.;Gitsov, L.; Aoshima, S.; Leduc, M.; Grubbs, R. B. Science 1995, 269,1080). Shortly afterwards, it was adapted to radical polymerizations byHawker et al. (Hawker, C. J.; Frechet, J. M. J.; Grubbs, R. B.,; Dao,J., J. Am. Chem. Soc. 1995, 117, 10763) and by Gaynor et al (Gaynor, S.G.; Edelman, S. Z.; Matyjaszewski, K., ACS PMSE Preprints 1996, 74;Gaynor, S. G.; Edelman, S. Z.; Matyjaszewski, K. Macromolecules, 1996,29,1079).

Further, polymers containing polar groups, such as polyacrylonitrile(PAN) are prepared in general by a free radical polymerization method.W. Berger et al. (Makromol. Chem., Macromol. Symp., 1986, 3, 301),describes such a free radical polymerization method for PAN. However,the free radical polymerization of acrylonitrile (AN) does not produce apolymer with well defined structure and narrow polydispersity index.Further, such free radical polymerization method is not suitable for thepreparation of block copolymers.

Polyacrylonitrile has also been prepared by a polymerization methodusing an anionic initiator. Such a method is described by Sogah et al(Macromolecules, 1987, 20, 1473); in general, anionic polymerizationprovides for control of molecular weight distribution by means of the"living" nature of its propagating chain with monomers such as styrene,diene and most non-polar acrylic monomers. However, in thepolymerization of monomers with polar groups, such as acrylonitrile, thecarbanion initiator attacks the polar group thus losing part of the"living" nature of the polymerization method. These defects have beenpartly overcome by carrying out the polymerization at very lowtemperature; this condition, however, renders the process impracticalfor commercial production of polymers containing polar groups, such asPAN.

Further, Higashimura et al., (Macromolecules, 1993, 26, 744) hasdescribed "living" cationic polymerization of styrene with an initiatingsystem based on 1-phenylethyl chloride (1-PhEtCl) and tin tetrachloride(SnCl₄) in the presence of tetra-n-butyl ammonium chloride (n-Bu₄ NCl)in methylene chloride as solvent. In addition, polymers with a varietyof terminal functionalities can be obtained by "living" cationicpolymerization and some of the end functions may be useful forinitiating another polymerization to give block copolymers. Thus, welldefined block copolymers by the transformation of initiating sites from"living" cationic to anionic polymerization have been described byGadkari et al. (J. Appl. Polym. Sci., Appl. Polym. Symp., 1989, 44, 19),Liu et al. (J. Polym. Sci., A, Polym. Chem. 1993, 31, 1709); Nemes etal. (J. Macromol. Sci., 1991, A28, 311); Kennedy et al. (Macromolecules,1991, 24, 6567); Kitayama et al. (Polym. Bull. (Berlin) 1991, 26, 513);Ruth et al. (Polym. Prepr. 1993, 34, 479); Nomura et al. (Macromolecules1994, 27, 4853) and Nomura et al. (Macromolecules 1995, 28, 86). Thedisadvantage of these techniques is that they include numerous steps,and the number of monomers that can be used with any of theabove-described methods is limited to those which can be polymerized bycationic or anionic methods. However, none of the prior art processesresults in a polymer with as narrow polydispersity index as the presentinvention.

It is well known to those skilled in the art of polymers that when thepolydispersity index of a polymer is wide the polymer contains polymericsegments with substantial smaller and larger molecular weight segmentsthan the number average molecular weight of the polymer. On the onehand, low molecular weight segments have an adverse effect on physicalproperties of the polymer such as tensile strength, elongation andflexural madulus; while segments of very large molecular weight resultin high melt viscosity of the polymer and, thus, in inferiorprocessability of the polymer. Thus, there is a need for a polymer withwell defined and narrow polydispersity index.

Atom Transfer Radical Polymerization (ATRP) has been described by Wanget al (in J. Am. Chem. Soc., 1995, 36, 2973; and in Macromolecules,1995, 28, 7572). However, polar monomers, such as acrylonitrile, havenot been successfully polymerized by ATRP as of now.

Thus, there is a need for a method to prepare block or graft copolymerswith well defined lengths and or number of blocks or grafts that can betailor made and that a precise number of grafts can be grown from thepolymer backbone.

There is also a need for a controlled polymerization of polar monomers,such as acrylonitrile (AN) that can produce a polymer with a narrowpolydispersity index and under industrially acceptable conditions.

There is also a need for polymeric materials of controlled architectureand narrow polydispersity index that may optionally contain polar groupsthat enhance solvent resistance properties. There is, for instance, aneed for solvent resistant thermoplastic acrylate elastomers.Thermoplastic elastomers in the context of the present invention areblock copolymers consisting of at least two distinct polymeric segments(blocks), which are thermodynamically incompatible and have differentglass transition temperatures (Tg).

SUMMARY OF THE INVENTION

Accordingly, Applicants have discovered a novel method which produces ahomo- or co-polymer, which may be a block or a graft copolymer, andwhich may optionally contain at least one polar functional group; thecopolymer further exhibits a narrow polydispersity index (M_(w) /M_(n) ;where M_(w) is -the weight average molecular weight and M_(n) is thenumber average molecular weight); furthermore, this method can becarried out under conditions suitable for commercial utilization.Further, Applicants have discovered that when certain macroinitiatorsare synthesized and used in ATRP, well defined block and graftcopolymers can be obtained.

Thus, it is an other object of the present invention to provide a methodto synthesize block copolymers by transformation of "living" carbocationinto "living" radical polymerization.

It is another object of the present invention to provide a novel methodfor the synthesis of a macroinitiator for "living" radicalpolymerization and for the synthesis of a well defined block or graftcopolymer where the macroinitiator constitutes at least one segment ofthe block copolymer.

It is another object of the present invention to provide a method toprepare a polymer, optionally containing at least one polar group, suchas nitrile, which exhibits a narrow polydispersity index.

It is an other object of the present invention to provide a polymercomposition which optionally contains at least one polar group, andwhere the polymer exhibits a narrow polydispersity index. It is anotherobject of the present invention to provide a method for the preparationof a block copolymer, optionally comprising at least one polymer blocksegment containing at least one polar group, and where the blockcopolymer exhibits a narrow polydispersity index.

It is another object of the present invention to provide a method tosynthesize a branched or hyperbranched macromolecule by atom or grouptransfer radical polymerization.

It is a further object of the present invention to provide for a blockor graft copolymer of polysulfone, polyester, or functionalizedpolyolefins, such as the ones produced by Shell under the Kraton name.

Accordingly, there is provided a method for atom (or group) transferradical polymerization, encompassing the polymerization of a vinylmonomer in the presence of an initiating system, which includes: aninitiator having a radically transferrable atom or group, a transitionmetal compound, and a ligand; the polymerization forms a macroinitiatorof formula (I):

    (macromolecule)-(X).sub.n                                  (I)

wherein each X is a halogen atom and n is an integer of 1 to 100; thismacromonomer is then used in the presence of a vinyl monomer, atransition metal compound, and a ligand to form a block or graftcopolymer, exhibiting a well defined molecular architecture.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows kinetic and molecular weight behavior plots for thepolymerization of 2-ethylhexylacrylate by atom transfer radicalpolymerization.

FIG. 2 shows kinetic plots and molecular weight behavior for thepolymerization of N-butylacrylate by atom transfer radicalpolymerization.

FIG. 3 shows kinetic and molecular weight behavior plots for thepolymerization of acrylonitrile by atom transfer radical polymerization.

FIG. 4 shows number average molecular weight (M_(n)) polydispersityindex (M_(w) /M_(n)) versus conversion plots for the blockcopolymerization of acrylonitrile using Br- PEHA!-Br and Br- PBA!-Br asthe initiator in diphenylether (DPE).

FIG. 5 shows GPC chromatograms for PSt-Cl and PSt-b-PSt-Cl polymersshown in Table 5 (exp. 1-2).

FIG. 6 shows GPC chromatograms for PSt-Cl and PSt-b-PMA-Cl polymersshown in Table 5 (exp. 1 and 3).

FIG. 7 shows GPC chromatograms for PSt-Cl and PSt-b-PMMA-CL polymersshown in Table 5 (exp. 1 and 4).

FIG. 8 shows an ¹ H-NMR spectrum (CDCl₃) of PSt-b-PMA-Cl copolymersM_(n) (GPC)=6200, M_(w) /M_(n) =1.20, M_(n) (NMR)=6020!.

FIG. 9 shows an ¹ H-NMR spectrum (CDCl₃) of PSt-b-PMMA-Cl copolymersM_(n) (GPC)=11090, M_(w) /M_(n) =1.57, M_(n) (NMR)=10300!.

FIG. 10 shows GPC chromatograms for PSt-Cl and PSt-b-PMA-Cl polymersobtained by one pot polymerization. Experimental conditions identical tothose in Table 5 (exp. 1 and 3).

FIG. 11 shows an ¹ H-NMR spectrum of difunctional polymethylsiloxanemacroinitiator.

FIG. 12 shows GPC traces of a difunctional polysiloxane macromonomer andthe resulting copolymer with styrene.

FIG. 13 shows the M_(n) and polydispersity dependence on conversion forATRP of styrene with difunctional polysiloxane macromonomer.

FIG. 14 shows the ¹ H-NMR spectrum ofpolystyrene-b-polydimethylsiloxane-b-polystyrene block copolymerprepared by ATRP.

FIG. 15 shows GPC traces of polysulfone andpoly(styrene-b-sulfone-b-styrene).

FIG. 16 shows GPC traces of polysulfone and poly(butylacrylate-b-sulfone-b-butyl acrylate).

FIG. 17 shows a ¹ H-NMR spectrum of poly(styrene-b-sulfone-b-styrene).

FIG. 18 shows a ¹ H-NMR spectrum of polysulfone.

FIG. 19 shows a ¹ H-NMR spectrum of poly(butylacrylate-b-sulfone-b-butyl acrylate).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides for an atom (or group) transfer radicalpolymerization to form a homopolymer or a copolymer of a monomer,optionally containing at least one polar group, polymer (A). Thepolymerization is accomplished in accordance with the present inventionin the presence of an initiating system comprising components (i), (ii)and (iii), as described below, to form a polymer.

In addition, the present invention provides for the preparation of amacroinitiator, which can be used in place of component (i) of theinitiating system, thus providing for the formation of a block or graftcopolymer consisting of at least one block of the macroinitiating moietyand at least one block of polymer (A).

In addition, the present invention provides a method to synthesize novelblock or graft copolymers by transformation of a controlledcarbocationic polymerization into controlled radical polymerization.

Further, the present invention provides a method to synthesize branchedand hyperbranched macromolecules by atom transfer radicalpolymerization.

Further, the present invention provides for the synthesis of novelattachable macroinitiators.

In the context of the present application, the term "macromolecule"refers to a molecule containing a large number of monomeric units andhaving a number average molecular weight (M_(n)) of at least 500.Further, the term "macroinitiator" refers to a macromolecule having atleast one initiating site. The term "macromonomer" refers to amacromolecule having at least one polymerizable site. In addition, theterm "living" initiating moiety (anionic, cationic or radical) refers toan initiating moiety that substantially does not undergo terminationreaction and thus, polymerization continues until substantially all themonomer is exhausted.

Polymer (A) is a homopolymer, or a block or graft copolymer ofcopolymerizable monomers, optionally at least one of which contains atleast one polar group.

(I) Monomers

In the present invention any radically polymerizable alkene containing apolar group can serve as a monomer for polymerization. The preferredmonomers include those of the formula (II): ##STR2## wherein R¹ and R²are independently selected from the group consisting of H, halogen, CF₃,straight or branched alkyl of 1 to 20 carbon atoms (preferably from 1 to6 carbon atoms, more preferably from 1 to 4 carbon atoms), aryl,α,β-unsaturated straight or branched alkenyl or alkynyl of 2 to 10carbon atoms (preferably from 2 to 6 carbon atoms, more preferably from2 to 4 carbon atoms), α,β-unsaturated straight or branched alkenyl of 2to 6 carbon atoms (preferably vinyl) substituted (preferably at theα-position) with a halogen (preferably chlorine), C₃ -C₈ cycloalkyl,hetercyclyl, C(═Y)R⁵, C(═Y)NR⁶ R⁷ and YC(═Y)R⁸, where Y may be NR⁸ or O(preferably O), R⁵ is alkyl of from 1 to 20 carbon atoms, alkoxy of from1 to 20 carbon atoms, aryloxy or heterocyclyloxy, R⁶ and R⁷ areindependently H or alkyl of from 1 to 20 carbon atoms, or R⁶ and R⁷ maybe joined together to form an alkylene group of from 2 to 5 carbonatoms, thus forming a 3- to 6-membered ring, and R⁸ is H, straight orbranched C₁ -C₂₀ alkyl and aryl; and

R³ is selected from the group consisting of H, halogen (preferablyfluorine or chlorine), C₁ -C₆ (preferably C₁) alkyl, COOR⁹ (where R⁹ isH, an alkali metal, or a C₁ -C₆ alkyl group) or aryl; or

R¹ and R³ may be joined to form a group of the formula (CH₂)_(n') (whichmay be substituted with from 1 to 2n' halogen atoms or C₁ -C₄ alkylgroups) or C(═O)--Y--C(═O), where n' is from 2 to 6 (preferably 3 or 4)and Y is as defined above; or

R⁴ is the same as R¹ or R² or optionally R⁴ is a CN group;

at least two of R¹, R², and R³ are H or halogen.

In the context of the present application, the terms "alkyl", "alkenyl"and "alkynyl" refer to straight-chain or branched groups (except for Cland C₂ groups)

Furthermore, in the present application, "aryl" refers to phenyl,naphthyl, phenanthryl, phenalenyl, anthracenyl, triphenylenyl,fluoranthenyl, pyrenyl, pentacenyl, chrysenyl, naphthacenyl, hexaphenyl,picenyl and perylenyl (preferably phenyl and naphthyl), in which eachhydrogen atom may be replaced with alkyl of from 1 to 20 carbon atoms(preferably from 1 to 6 carbon atoms and more preferably methyl), alkylof from 1 to 20 carbon atoms (preferably from 1 to 6 carbon atoms andmore preferably methyl) in which each of the hydrogen atoms isindependently replaced by a halide (preferably a fluoride or achloride), alkenyl of from 2 to 20 carbon atoms, alkynyl of from 1 to 20carbon atoms, alkoxy of from 1 to 6 carbon atoms, alkylthio of from 1 to6 carbon atoms, C₃ -C₈ cycloalkyl, phenyl, halogen, NH₂, C₁ -C₆-alkylamino, C₁ -C₆ -dialkylamino, and phenyl which may be substitutedwith from 1 to 5 halogen atoms and/or C_(l) -C₄ alkyl groups. (Thisdefinition of "aryl" also applies to the aryl groups in "aryloxy" and"aralkyl.") Thus, phenyl may be substituted from 1 to 5 times andnaphthyl may be substituted from 1 to 7 times (preferably, any arylgroup, if substituted, is substituted from 1 to 3 times) with one of theabove substituents. More preferably, "aryl" refers to phenyl, naphthyl,phenyl substituted from 1 to 5 times with fluorine or chlorine, andphenyl substituted from 1 to 3 times with a substituent selected fromthe group consisting of alkyl of from 1 to 6 carbon atoms, alkoxy offrom 1 to 4 carbon atoms and phenyl. Most preferably, "aryl" refers tophenyl and tolyl.

In the context of the present invention, "heterocyclyl" refers topyridyl, furyl, pyrrolyl, thienyl, imidazolyl, pyrazolyl, pyrazinyl,pyrimidinyl, pyridazinyl, pyranyl, indolyl, isoindolyl, indazolyl,benzofuryl, isobenzofuryl, benzothienyl, isobenzothienyl, chromenyl,xanthenyl, purinyl, pteridinyl, quinolyl, isoquinolyl, phthalazinyl,quinazolinyl, quinoxalinyl, naphthyridinyl, phenoxathiinyl, carbazolyl,cinnolinyl, phenanthridinyl, acridinyl, 1,10-phenanthrolinyl,phenazinyl, phenoxazinyl, phenothiazinyl, oxazolyl, thiazolyl,isoxazolyl, isothiazolyl, and hydrogenated forms thereof known to thosein the art. Preferred heterocyclyl groups include pyridyl, furyl,pyrrolyl, thienyl, imidazolyl, pyrazolyl, pyrazinyl, pyrimidinyl,pyridazinyl, pyranyl and indolyl, the most preferred heterocyclyl groupbeing pyridyl. Accordingly, suitable vinyl heterocycles to be used as amonomer in the present invention include 2-vinyl pyridine, 4-vinylpyridine, 2-vinyl pyrrole, 3-vinyl pyrrole, 2-vinyl oxazole, 4-vinyloxazole, 5-vinyl oxazole, 2-vinyl thiazole, 4-vinyl thiazole, 5-vinylthiazole, 2-vinyl imidazole, 4-vinyl imidazole, 3-vinyl pyrazole,4-vinyl pyrazole, 3-vinyl pyridazine, 4-vinyl pyridazine, 3-vinylisoxazole, 3-vinyl isothiazoles, 2-vinyl pyrimidine, 4-vinyl pyrimidine,5-vinyl pyrimidine, and any vinyl pyrazine, the most preferred being2-vinyl pyridine. The vinyl heterocycles mentioned above may bear one ormore (preferably 1 or 2) C₁ -C₆ alkyl or alkoxy groups, cyano groups,ester groups or halogen atoms, either on the vinyl group or theheterocyclyl group, but preferably on the heterocyclyl group. Further,those vinyl heterocycles which, when unsubstituted, contain an N--Hgroup may be protected at that position with a conventional blocking orprotecting group, such as a C₁ -C₆ alkyl group, a tris-C₁ -C₆ alkylsilylgroup, an acyl group of the formula R¹⁰ CO (where R¹⁰ is alkyl of from 1to 20 carbon atoms, in which each of the hydrogen atoms may beindependently replaced by halide, preferably fluoride or chloride),alkenyl of from 2 to 20 carbon atoms (preferably vinyl), alkynyl of from2 to 10 carbon atoms (preferably acetylenyl), phenyl which may besubstituted with from 1 to 5 halogen atoms or alkyl groups of from 1 to4 carbon atoms, or aralkyl (aryl-substituted alkyl, in which the arylgroup is phenyl or substituted phenyl and the alkyl group is from 1 to 6carbon atoms), etc. (This definition of "heterocyclyl" also applies tothe heterocyclyl groups in "heterocyclyloxy" and "heterocyclic ring.")

More specifically, preferred monomers include (but not limited to)styrene, p-chloromethylstyrene, vinyl chloroacetate, acrylate andmethacrylate esters of C₁ -C₂₀ alcohols, isobutene,2-(2-bromopropionoxy) ethyl acrylate, acrylonitrile, andmethacrylonitrile.

The monomer containing at least one polar group may be present in anamount of 5 to 100 wt % by weight based on the total amount of monomers.A preferred amount of the monomer containing at least one polar group is10 to 100 wt %; the most preferred amount is 20 to 100 wt % based on thetotal amount of monomers. This is particularly important in the case ofacrylonitrile because an amount of at least 20 wt % assures solventresistance properties of the resulting polymer A.

(II) Initiating System

The initiating system for the atom or group transfer radicalpolymerization of the present invention containing components (i), (ii)and (iii) as described below.

component (i)--initiator

Suitable initiators include those of the formula (III):

    R.sup.11 R.sup.12 R.sup.13 C--Z'                           (III)

where:

Z' is selected from the group consisting of Cl, Br, I, OR¹⁰ (as definedabove), SR¹⁴, SeR¹⁴, --SCN (thiocyanate) OC(═O)R¹⁴, OP(═O)R¹⁴, OP(═O)(OR¹⁴)₂, OP(═O)OR¹⁴, O--N(R¹⁴)₂ and S--C(═S)N(R¹⁴)₂, where R¹⁴ is arylor a straight or branched C₁ -C₂₀ (preferably C₁ -C₁₀) alkyl group, orwhen an N(R¹⁴)₂ group is present, the two R¹⁴ groups may be joined toform a 5-, 6- or 7-membered heterocyclic ring (in accordance with thedefinition of "heterocyclyl" above); and

R¹¹, R¹² and R¹³ are each independently selected from the groupconsisting of H, halogen, C₁ -C₂₀ alkyl (preferably C₁ -C₁₀ alkyl andmore preferably C₁ -C₆ alkyl), C₃ -C₈ cycloalkyl, C(═Y)R⁵, C(═Y)NR⁶ R⁷(where R⁵ -R⁷ are as defined above), COCl, OH (preferably only one ofR¹¹, R¹² and R¹³ is OH), CN, C₂ -C₂₀ alkenyl or alkynyl (preferably C₂-C₆ alkenyl or alkynyl, and more preferably vinyl), oxiranyl, glycidyl,aryl, heterocyclyl, aralkyl, aralkenyl (aryl-substituted alkenyl, wherearyl is as defined above, and alkenyl is vinyl which may be substitutedwith one or two C₁ -C₆ alkyl groups and/or halogen atoms, preferablychlorine), C₁ -C₆ alkyl in which from 1 to all of the hydrogen atoms(preferably 1) are replaced with halogen (preferably fluorine orchlorine where 1 or more hydrogen atoms are replaced, and preferablyfluorine, chlorine or bromine where 1 hydrogen atom is replaced) and C₁-C₆ alkyl substituted with from 1 to 3 substituents (preferably 1)selected from the group consisting of C₁ -C₄ alkoxy, aryl, heterocyclyl,C(═Y)R⁵ (where R⁵ is as defined above), C(═Y)NR⁶ R⁷ (where R⁶ and R⁷ areas defined above), oxiranyl and glycidyl; such that no more than two ofR¹¹, R¹² and R¹³ are H (preferably no more than one of R¹¹, R¹² and R¹³is H).

In the present initiator, X is preferably Cl or Br.

When an alkyl, cycloalkyl, or alkyl-substituted aryl group is selectedfor one of R¹¹, R12 and R¹³, the alkyl group may be further substitutedwith an X group as defined above. Thus, it is possible for the initiatorto serve as a starting molecule for branch or star (co)polymers.Preferred example is where one of R¹¹, R¹² and R¹³ is phenyl substitutedwith from one to five C₁ -C₆ alkyl substituents, each of which mayindependently be further substituted with a X group (e.g.,α,α'-dibromoxylene, hexakis(α-chloro- or α-bromomethyl)-benzene).

Preferred initiators include 1-phenylethyl chloride and 1-phenylethylbromide (e.g., where R¹¹ =Ph, R¹² =CH₃, R¹³ =H and X=Cl or Br),chloroform, carbon tetrachloride, 2-bromopropionitrile, C₁ -C₆ -alkylesters of a 2-halo-C₁ -C₆ -carboxylic acid (such as 2-chloropropionicacid, 2-bromopropionic acid, 2-chloroisobutyric acid, 2-bromoisobutyricacid, etc.) and compounds of the formula C₆ H_(x) (CH₂ Y')Y, where Y' isCl or Br, x+y=6 and y >1. More preferred initiators include1-phenylethyl chloride, 1-phenylethyl bromide, methyl2-chloropropionate, ethyl 2-chloropropionate, methyl 2-bromopropionate,ethyl 2-bromoisobutyrate, 60 ,α'-dichloroxylene, α,α'-dibromoxylene andhexakis(α-bromomethyl)benzene. The initiator, in accordance with thepresent invention, is exemplified (but not limited to) an alkyl halide,aralkyl halide or haloalkyl ester. Generally, an aromatic halide such asα,α'-dihalo-p-xylene, benzyl halide, 1-phenylethyl halide andα-haloacrylate are suitable initiators. However, initiators with a cyanogroup such as haloacetonitrile or halopropionitrile are more effectivein the preparation of polymer (A) with narrow polydispersity index. Inaddition, although any of the halogens is suitable as the halide part ofthe initiator according to the present invention, bromine or chlorineare preferred.

component (ii)--transition metal compound

Any transition metal compound which can participate in a redox cyclewith the initiator and dormant polymer chain, but which does not form adirect carbon-metal bond with the polymer chain, is suitable for use inthe present invention. Preferred transition metal compounds are those ofthe formula M_(t) ^(n+) X'_(n), where:

M_(t) ^(n+) may be selected from the group consisting of Cu¹⁺, CU²⁺,Fe²⁺, Fe³⁺, Ru²⁺, Ru³⁺, Cr²⁺, Cr³⁺, Mo⁰, Mo³⁺, W²⁺, Mo⁺, Mo²⁺, W³⁺,Rh³⁺, Rh⁴⁺, Co⁺, Co²⁺, Re²⁺, Re³⁺, Ni⁰, Ni⁺, Mn³⁺, Mn⁴⁺, V²⁺, V³⁺, Zn⁺,Zn²⁺, Au⁺, Au²⁺, Ag⁺ and Ag²⁺ ;

X' is selected from the group consisting of halogen, C₁ -C₂₀ -alkoxy,(SO₄)_(1/2), (PO₄)_(1/3), (HPO₄)_(1/2), (H₂ PO₄), triflat SCN(thiocyanate), hexafluorophosphate, alkylsulfonate, arylsulfonate(preferably benzenesulfonate or toluenesulfonate), SeR¹⁴, CN and R¹⁵CO₂, where R¹⁴ is as defined above and R¹⁵ is H or a straight orbranched C₁ -C₂₀ alkyl group (preferably methyl), a benzoic acidderivative, aryl or a heteroaryl group which may be substituted from 1to 5 times with a halogen (preferably 1 to 3 times with fluorine orchlorine); and n is the formal charge on the metal (e.g., 0≦n≦7). Ascomponent (ii) a transition metal halide is required. Although anytransition metal is suitable in the present invention, a preferredtransition metal (but not limited to) is Cu(I). Likewise, the preferredcounter ion for the transition metal is chlorine or bromine.

component (iii)--ligand

Suitable ligands for use in the present invention include ligands havingone or more nitrogen, oxygen, phosphorus and/or sulfur atoms which cancoordinate to the transition metal through a σ-bond, and ligandscontaining two or more carbon atoms which can coordinate to thetransition metal through a π-bond. However, preferred N--, O--, P-- andS-- containing ligands may have one of the following formulas:

    R.sup.16 --Z'--R.sup.17

    R.sup.16 --Z'--(R.sup.18 --Z').sub.m --R.sup.17

where:

R¹⁶ and R¹⁷ are independently selected from the group consisting of H,C₁ -C₂₀ alkyl, aryl, heterocyclyl, and C₁ -C₆ alkyl substituted with C₁-C₆ alkoxy, C₁ -C₄ dialkylamino, C(═Y)R⁵, C(═Y)R⁶ R⁷ and YC(═Y)R⁸, whereY, R⁵, R⁶, R⁷ and R⁸ are as defined above; or

R¹⁶ and R¹⁷ can be joined to form a saturated, unsaturated orheterocyclic ring as described above for the "heterocyclyl" group;

Z' is O, S, NR¹⁹ or PR¹⁹, where R¹⁹ is selected from the same group asR¹⁶ and R¹⁷,

each R¹⁸ is independently a divalent group selected from the groupconsisting of C₂ -C₄ alkylene (alkanediyl) and C₂ -C₄ alkenylene wherethe covalent bonds to each Z' are at vicinal positions (e.g., in a1,2-arrangement) or at β-positions (e.g., in a 1,3-arrangement), andfrom C₃ -C₈ cycloalkanediyl, C₃ -C₈ cycloalkenediyl, arenediyl andheterocyclylene where the covalent bonds to each Z are at vicinalpositions; and

m is from 1 to 6.

In addition to the above ligands, each of R¹⁶ --Z' and R¹⁷ --Z' can forma ring with the R¹⁸ group to which the Z' is bound to form a linked orfused heterocyclic ring system (such as is described above for"heterocyclyl"). Alternatively, when R¹⁶ and/or R¹⁷ are heterocyclyl, Z'can be a covalent bond (which may be single or double), CH₂ or a 4- to7-membered ring fused to R¹⁶ and/or R¹⁷, in addition to the definitionsgiven above for Z'. Exemplary ring systems for the present ligandinclude bipyridine, bipyrrole, 1,10-phenanthroline, a cryptand, a crownether, etc., where Z' is PR¹⁹, R¹⁹ can also be C₁ -C₂₀ -alkoxy.

Included as suitable ligands are pyridine derivatives which containsubstituents in the 2 or 2 and 6 position such as a carbonyl containingmoiety, an imine containing moiety or a thioketone containing moiety.

Also included as suitable ligands in the present invention are CO(carbon monoxide), porphyrins and porphycenes, the latter two of whichmay be substituted with from 1 to 6 (preferably from 1 to 4) halogenatoms, C₁ -C₆ alkyl groups, C₁ -C₆ -alkoxy groups, C₁ -C₆alkoxycarbonyl, aryl groups, heterocyclyl groups, and C₁ -C₆ alkylgroups further substituted with from 1 to 3 halogens.

Further ligands suitable for use in the present invention includecompounds of the formula R²⁰ R²¹ C(C(═Y)R⁵)₂, where Y and R⁵ are asdefined above, and each of R²⁰ and R²¹ is independently selected fromthe group consisting of H, halogen, C₁ -C₂₀ alkyl, aryl andheterocyclyl, and R²⁰ and R²¹ may be joined to form a C₃ -C₈ cycloalkylring or a hydrogenated (i.e., reduced, non-aromatic or partially orfully saturated) aromatic or heterocyclic ring (consistent with thedefinitions of "aryl" and "heterocyclyl" above), any of which (exceptfor H and halogen) may be further substituted with 1 to 5 and preferably1 to 3 C₁ -C₆ alkyl groups, C₁ -C₆ alkoxy groups, halogen atoms and/oraryl groups. Preferably, one of R²⁰ and R²¹ is H or a negative charge.

Additional suitable ligands include, for example, ethylenediamine andpropylenediamine, both of which may be substituted from one to fourtimes on the amino nitrogen atom with a C₁ -C₄ alkyl group or acarboxymethyl group; aminoethanol and aminopropanol, both of which maybe substituted from one to three times on the oxygen and/or nitrogenatom with a C₁ -C₄ alkyl group; ethylene glycol and propylene glycol,both of which may be substituted one or two times on the oxygen atomswith a C₁ -C₄ alkyl group; diglyme, triglyme, tetraglyme, etc.

Suitable carbon-based ligands include arenes (as described above for the"aryl" group) and the cyclopentadienyl ligand. Preferred carbon-basedligands include benzene (which may be substituted with from one to sixC₁ -C₄ alkyl groups, e.g., methyl) and cyclopentadienyl (which may besubstituted with from one to five methyl groups, or which may be linkedthrough an ethylene or propylene chain to a second cyclopentadienylligand). Where the cyclopentadienyl ligand is used, it may not benecessary to include a counteranion (X') in the transition metalcompound.

Preferred ligands include unsubstituted and substituted pyridines andbipyridines (where the substituted pyridines and bipyridines are asdescribed above for "heterocyclyl"), acetonitrile, (R¹⁰ O)₃ P, PR¹⁰ ₃,1,10-phenanthroline, porphyrin, cryptands such as K₂₂₂, crown etherssuch as 18-crown-6, and nitrogen or sulfur analogs of crown ethers. Themost preferred ligands are substituted bipyridine, bipyridine and (R¹⁰O)₃ P. Examples of such ligands (but not limited to) are2,2'-bipyridine, a p-alkyl substituted derivative of the 2,2'-bipyridineor a p-alkoxy substituted derivative of the 2,2'-bipyridine.

The mole ratio of the components (i), (ii) and (iii) of the initiatingsystem may range from 1/0.01/0.02 to 1/4/12; the preferred range howeveris 1/0.1/0.2 to 1/2/6.

In accordance with the present invention, the components (i), (ii) and(iii) of the initiating system are introduced to a reactor, the reactoris subsequently degassed under vacuum and charged with an inert gas,such as argon. No particular order in the addition of the abovecomponents of the initiating system is required. A monomer and,optionally, a solvent is then added to the reactor through a rubberseptum.

The preferred polymerization temperature to prepare polymer (A) withnarrow polydispersity index, in accordance with the present invention,is 0° C. to 150° C.; it is preferred to use a reaction temperature belowthe boiling point of the polar group containing monomer, where a narrowpolydispersity index is achieved and a loss of the polar groupcontaining monomer is minimized.

The present polymerization may be conducted in the absence of solvent("bulk" polymerization). However, when a solvent is used, suitablesolvents include ethers, cyclic ethers, alkyl esters, aryl esters, C₅-C₁₀ alkanes, C₁ -C₈ cycloalkanes which may be substituted with from 1to 3 C₁ -C₄ alkyl groups, aromatic hydrocarbon solvents, halogenatedhydrocarbon solvents, acetonitrile, dimethylformamide, mixtures of suchsolvents, and supercritical solvents (such as CO₂, C₁ -C₄ alkanes inwhich any H may be replaced with F, etc.). The present polymerizationmay also be conducted in accordance with known suspension, emulsion andprecipitation polymerization processes.

Suitable ethers include compounds of the formula R²² OR²³, in which eachof R²² and R²³ is independently an alkyl group of from 1 to 6 carbonatoms which may be further substituted with a C₁ -C₄ -alkoxy group.Preferably, when one of R²² and R²³ is methyl, the other of R²² and R²³is alkyl of from 4 to 6 carbon atoms or C₁ -C₄ -alkoxyethyl. Examplesinclude diethyl ether, ethyl propyl ether, dipropyl ether, methylt-butyl ether, di-t-butyl ether, glyme (dimethoxyethane), diglyme(diethylene glycol dimethyl ether), etc.

Suitable cyclic ethers include THF and dioxane. Suitable aromatichydrocarbon solvents include benzene, toluene, o-xylene, m-xylene,p-xylene and any isomer or mixture of isomers of cumene. Suitablehalogenated hydrocarbon solvents include CH₂ Cl₂, 1,2-dichloroethane andbenzene substituted from 1 to 6 times with fluorine and/or chlorine,although one should ensure that the selected halogenated hydrocarbonsolvent(s) does not act as an initiator under the reaction conditions.

A solvent suitable for the preparation of polymer (A) of the presentinvention must meet the following requirements: it must have low chaintransfer constant (as defined in: Polymer Handbook, third edition, J.Brandrup and E. H. Immergut, Editors, II/81); be able to dissolve theinitiating system; and must not form a complex with the initiatingsystem. Examples of solvents suitable for the present invention (but notlimited to) are: diphenylether, diaryl ether, dimethoxybenzene,propylene carbonate, and ethylene carbonate. Especially useful solventsin accordance with the present invention are propylene carbonate andethylene carbonate which result in polymer (A) exhibiting narrowpolydispersity index.

III)--Use of Macroinitiator for ATRP

(a) In situ Generation of a Macroinitiator

(i) Transformation of "Living" Carbocationic to "living" RadicalPolymerization

A further object of the present invention is to synthesize a blockcopolymer by combining a "living" carbocationic polymerization with a"living" radical polymerization. "Living" cationic polymerizations havebeen described by Matyjaszewski (Cationic Polymerizations, Mechanism,Synthesis and Applications; Marcel Dekker, Inc., New York, 1996). Thus,a macromonomer can be synthesized by a "living" carbocationic method,having a terminal group, such as a halogen group, which subsequently canbe used as an effective macroinitiator in a "living" atom or grouptransfer radical polymerization. Scheme 3(a) exemplifies the procedure(not limited to the particular examples) for the synthesis ofpoly(styrene-b-styrene), poly(styrene-b-methylacrylate) andpoly(styrene-b-methylmethacrylate) copolymers. In addition, asexemplified in Scheme 3(b), a variety of ABA block copolymers withpolyisobutene (PIB) mid block can be prepared. ##STR3##

(ii) Synthesis of macroinitiator by polyesterification

1) In situ polycondensation of a monofunctional acid and acid halidecontaining an activated halogen atom.

An example is the polyesterification of a diol (1.0 mol) with a diacid(0.95 mol) in the presence of 2-bromopropionic acid or chloroacetic acid(0.05 mol) to produce a polyester having a degree of polymerization(DP)=20 and α-halogen end group.

(b) Polymer Modification to Generate a Macroinitiator

Another object of the present invention is to synthesize a novel blockcopolymer using a novel atom or group transfer radical polymerizationinitiator.

Thus, according to the present invention, a compound of formula (IV):

    Y.sub.1 --R.sub.3 --R.sub.3 '--(X.sub.3).sub.n             (IV)

is reacted with a macromonomer that is functionalized with a group C.The functional group C must be able to react with Y₁ to form a stablebond and thus the functional group X₃ is now added to the macromonomer.The addition of the group X₃ to the macromonomer transforms the monomerinto a macroinitiator for ATRP. This macroinitiator is used as component(i) of the initiating system to polymerize a vinyl monomer in thepresence a transition metal compound (component (ii)), and a ligand(component (iii)) to form a block copolymer. In formula (IV), X₃ is ahalogen (preferentially chlorine or bromine), n is an integer of 1 to100, preferentially of 1 to 10, Y₁ is any functional group such as (butnot limited to) hydroxyl, carboxyl, amine, --SiH or --C(═O)--X, where Xis a halogen. R₃ is selected from the group consisting of alkyl, aryland aralkyl group, as defined above, and R₃ ' is a C₁ -C₂₀ -alkyl group.

This novel method for the preparation of a block copolymer can best beunderstood in the scheme 4 below: ##STR4##

Suitable macrooinitiators are macrromomers containing at least onefunctionality such as (but not limited to) hydroxyl, carboxyl, vinyl,amine or thiol. Preferred monomers are acrylic and methacrylic acidesters having from 1 to about 20 carbon atoms in the alcohol moiety,styrene, vinyl substituted styrene, such as α-alkyl styrene or ringsubstituted styrene such as p-alkyl styrene; such monomers arecommercially available or can be easily prepared by known esterificationprocesses. Preferred esters are n-butyl acrylate, ethyl acrylate, methylmethacrylate, isobornyl methacrylate and 2-ethylhexyl acrylate;preferred styrenic monomers are styrene, α-methyl styrene, p-methylstyrene, p-tert-butyl styrene, p-acetoxy styrene and ring-halogenatedstyrene.

The following exemplify (but are not limited to) methods of synthesis ofmultifunctional polymers which can be used in the synthesis of block andgraft copolymers in accordance with the rpesent invention.

1) Esterification of hydroxy and phenoxy end groups with halo acidhalide.

An Example in accordance with this object is polysulfone prepared withan excess of Bisphenol A, esterified with excess of 2-bromopropionylbromide to provide a polymer with two bromopropionyl end groups.

2) Incorporation of benzyl chloride end groups by hydrosilation process.

A polymer containing two unsaturated end groups at both ends,exemplified by a divinyl terminated polydimethylsiloxane (PDMS), isreacted with H-SiMe₂ -PhOCH₂ -Cl in the presence of Pt catalyst.

3) Polydimethylsiloxane (PDMS) containing Si-H groups at the terminal oras pendant units is reacted with p-chloromethylstyrene (p-ClmeSt) in thepresence of Pt catalyst to yield PDMS with terminal or pendant benzylchloride groups.

The resulting polymer can be presented by:

(macromolecule)--(X₁)_(n)

where X₁ is a halogen and n is an integer of from 1 to 100,preferentially from 1 to 10. Thus, the resulting halogenatedmacromolecule can subsequently be used as component (i) of theinitiating system for the preparation of a polymer optionally containingat least one polar group; the result of the polymerization with theabove-discussed macroinitiator may be an ABA block copolymer with theend blocks being a vinyl polymer and the middle block being any polymer.

Examples of novel block or graft copolymers produced by macroinitiatorsin accordance with the present invention include (but are not limitedto) block copolymers containing a block moiety of polysiloxane,polyester, polysulfone or polyamide, or ethylene/butylene copolymer suchas the ones produced by Shell under the Kraton name.

II. AB₂ Monomers and their Use in ATRP

AB₂ monomer is defined as a hybrid molecule containing polymerizabledouble bond (B₂) and an atom or group (A) which can be cleavedhomolytically and reversibly.

Atom Transfer Radical Polymerization (ATRP) allows for the controlledradical polymerization of (meth)acrylic esters, (meth)acrylonitrile,dienes and styrenic monomers. For AB₂ monomers to be used in ATRP, it isrequired that they have the basic structure of B-R-F, where B is thepolymerizable double bond, R is an organic spacer group, and F is afunctional group containing a halogen atom which can be homolytically,yet reversibly, cleaved by reaction with copper(I) salts. For example,the B group can be methacrylic, acrylic, or styrenic in nature. The Fgroup could be a benzylic halide, 2-halopropionate, etc. The versatilityof this approach is enhanced by the wide variety of R groups that can beinserted between the double bond and the functional group.

Acrylic AB₂ monomers can be synthesized by the reaction of, for example(but not limited to), 2-hydroxyethyl acrylate or 2-hydroxyethylmethacrylate with an acid halide, either 2-bromopropionyl bromide,2-bromoisobutyryl bromide, or chloroacetyl chloride.

The homolytic cleavage of group A can occur at the stage of monomer,polymer or both. Group A becomes group A' when it is pendent or A" whenit is at the chain end of a macromonomer. Thus, the followingpossibilities can occur depending on the relative reactivities of A, A'and A":

a) Description of Reactivity of A-group

(i) Homopolymerization

1) Reactivity of group A in monomer is similar to reactivity of groupsA' and A" in the polymer.

Examples include (but are not limited to) ATRP of p-chloromethylstyrene,2-(2-bromopropionoxy)ethyl acrylate, etc., which result in ahyperbranched structure with cluster ("grape bunch") structure.

2) Reactivity of A >>A' (no A" but reactivity A˜A")

Examples include (but are not limited to) ATRP ofp-chlorosulfonylstyrene, vinyl chloroacetate, etc., which result in alinear "condensation" polymer with pendant A" groups.

3) Reactivity of A=A'; no A"

Examples include (but are not limited to) free radical polymerization(FRP) of p-chloromethylstyrene, 2-(2-bromopropionoxy) ethyl acrylate,etc., which result in a linear conventional free radical polymer withpendant A' groups.

4) Reactivity of A<<A'<A"

Examples include (but are not limited to) ATRP of chloroacrylates,chloroacrylonitrile, etc., which result in a nearly perfect dendriticstructure (no cluster due to lack of terminal B₂ bonds)

Polymers 1-4 above are reacted with styrene, (meth)acrylate, oracrylonitrile, etc. to yield block and graft copolymers by the processof the present invention. The polydispersity of the resulting copolymeris: M_(w) /M_(n) =1.1 to 3.0.

(ii) Simultaneous copolymerization of AB₂ monomer with a conventionalvinyl monomer

1) Reactivity of group A in monomer is similar to reactivity of groupsA'and A" in the polymer.

Examples include (but are not limited to) ATRP ofstyrene/p-chloromethylstyrene, butyl acrylate/2-(2-bromopropionoxy)ethylacrylate, etc. The resulting polymers have branched structure withcluster ("grape bunch") structure; branch density depends on comonomerratio.

2) Reactivity of A >>A' (no A" but reactivity A˜A")

Examples include (but are not limited to) ATRP ofp-chlorosulfonylstyrene, vinyl chloroacetate, with styrene, etc., whichresult in macromonomers with vinyl acetate(VAc), branched structurespossibly with p-chlorosulfonylstyrene.

3) Reactivity of A=A'; no A"

Examples include (but are not limited to) free radical polymerization(FRP) of p-chloromethylstyrene, 2-(2-bromopropionoxy)ethyl acrylate,etc., with e.g., styrene, which result in a linear conventional freeradical (FR) polymer with a few pendant A' groups

4) Reactivity of A<<A'<A"

Examples include (but are not limited to) ATRP of chloroacrylates,chloroacrylonitrile, acrylonitrile, (meth)acrylate esters, etc., withe.g., styrene which result substantially in nearly perfect dendriticstructure (no cluster due to lack of terminal B₂ bonds) with a two layershape due to differences in reactivity of chloroacrylates and styrene;spontaneous star like block copolymer

(iii) Consecutive copolymerization

1) Reactivity of group A in monomer is similar to reactivity of groupsA' and A" in the polymer.

Representative examples include (but are not limited to) ATRP ofp-chloromethylstyrene, 2-(2-bromopropionoxy)ethyl acrylate, etc.,followed by styrene or butyl acrylate. The result is a substantiallyhyperbranched core with cluster ("grape bunch") structure, star-likesecond layer which can be soft (low Tg segment) or soft followed by hard(high Tg) segment. Another possibility is a free radical (FR)copolymerization of p-chloromethylstyrene (pClMeSt) with styrene orbutylacrylate/2-(2-bromopropionoxy) ethyl acrylate and then graftingfrom the backbone to get a graft copolymer.

2) Reactivity of A>>A' (no A" but reactivity A˜A")

Examples include (but are not limited to) ATRP of vinyl chloroacetatewith styrene, etc. This results in the formation of a macromonomer ofpolystyrene with a vinyl acetate end group. Another possibility is afree radical copolymerization of VClAc with VAc and then grafting fromthe backbone.

3) Reactivity of A=A'; no A"

Examples are the free radical polymerization (FRP) ofp-chloromethylstyrene, 2-(2-bromopropionoxy)ethyl acrylate, etc, withe.g., butyl acrylate. The result is a linear free radical polymer with afew pendant A' groups. Subsequent polymerization of the second monomerby ATRP results in the formation of a comb/graft copolymer.

4) Reactivity of A<<A'<A"

Example include (but are not limited to) ATRP of chloroacrylates,chloroacrylonitrile, etc., initiated by an initiator such as sulfonylchloride, chloromalonate, and optionally additional monomer such asstyrene. The result is a nearly perfect dentritic structure (no clusterdue to lack of terminal B₂ bonds) with a two layer shape due todifferences in reactivity of chloroacrylates and styrene. Several layersof star like block copolymers can be grown.

Some examples of polymeric architecture obtained by a polymerization inaccordance with the present invention follow:

(b) Hyperbranched Polymers

In this object of the present invention the AB₂ molecule can bepresented by formula V ##STR5## wherein R¹, R², and R³ are as previouslydescribed and R₂ ⁴ is an organic spacer group and A is selected from thegroup consisting of R₂ ⁴ '--X and X, where X is a halogen (preferablychlorine or bromine), and R₂ ⁴, is selected from the group consisting ofstraight or branched alkyl of from 1 to 20 carbon atoms (preferably from1 to 6 carbon atoms, more preferably from 1 to 4 carbon atoms),α,β-unsaturated straight or branched alkenyl or alkynyl of 2 to 10carbon atoms (preferably from 2 to 6 carbon atoms, more preferably from2 to 4 carbon atoms), α,β-unsaturated straight or branched alkenyl of 2to 6 carbon atoms (preferably vinyl) substituted (preferably at theα-position) with a halogen (preferably chlorine), C₃ -C₈ cycloalkyl,benzyl, hetercyclyl, C(═Y)R⁵, C(═Y)NR⁶ R⁷ and YC(═Y)R⁸, C(═Y)--Y--R⁵--C(═Y)--R⁸ where Y may be NR⁸ or O (preferably O), R⁵ is alkyl of from1 to 20 carbon atoms, alkoxy of from 1 to 20 carbon atoms, aryloxy orheterocyclyloxy, R⁶ and R⁷ are independently H or alkyl of from 1 to 20carbon atoms, or R⁶ and R⁷ may be joined together to form an alkylenegroup of from 2 to 5 carbon atoms, thus forming a 3- to 6-membered ring,and R⁸ is H, straight or branched C₁ -C₂₀ alkyl or aryl; and

R¹ and R³ may be joined to form a group of the formula (CH₂)_(n), (whichmay be substituted with from 1 to 2n' halogen atoms or C₁ -C₄ alkylgroups) or C(═O)--Y--C(═O), where n' is from 2 to 6 (preferably 3 or 4)and Y is as defined above.

Preferred monomers (but not limited to) are p-chloromethylstyrene (CMS),methyl-α-chloroacrylate and 2-(2-bromopropionoxy) ethyl acrylate.

The method, in accordance with the present invention, for making ahyperbranched molecule is illustrated below in scheme 5: ##STR6## whereR represents an alkyl or any ester, and X is a functional group(preferentially a halogen).

In scheme 5, the activation-deactivation process is shown in the firststep and is assumed to occur throughout the polymerization. Activationoccurs prior to addition of a monomer unit and deactivation aftermonomer addition.

Subsequent to the activation of a monomer a second monomer is added. Theresulting dimer can then be activated at either site and add anadditional monomer. As the new monomer is added, forming a trimer,another functional site is added to the growing macromolecule. Eachfunctional group can be activated by Cu(I) and add additional monomerunits. By repetition of this process, a hyperbranched polymer isobtained. It should be noted that each macromoloecule has one doublebond and nX groups, where n equals the number of repeated units. Due tothe presence of the double bond in the macromoloecule, themacromoloecule can be incorporated into another macromoloecule, similarto a step growth polymerization. In scheme 1, a molecule is advancedfrom a trimer to an octamer by addition of any combination of fiverepeat units, i.e., five monomers, a dimer or a trimer etc.

If a hyperbranched polymer is dissolved in a conventional monomer, andthen activated with Cu(I), a linear chain of the second monomer can growoff the hyperbranched macromolecule. When the hyperbranchedmacromolecule is a multi-armed initiator, the resulting copolymer is amulti-armed star copolymer.

(c) Branched Polymers

When a monomer of formula (IV) is polymerized with a conventional vinylmonomer such as styrene, the density of the branched polymer can beattenuated by changing the amount of branching monomer used.

Scheme 6, shows the chain growth, for a copolymerization of an AB₂monomer with a conventional vinyl monomer. ##STR7## where R' is amonomer and X is a functional group (preferentially halogen); n is aninteger of 1 to 1,000,000.

Initiation, that is the activation of a halide functional group andaddition of a monomer, is fast. Fast initiation results in the formationof polymer chain (propagation) with vinyl end groups which can beincorporated into other polymer chains (branching). The rate of chainincorporation depends upon the r₁ and r₂ values for the respectivemonomer and the polymerizable chain-end functionality on themacromonomer (B₂); (reactivity ratios, "r" are defined in: PolymerHandbook, third edition, J. Brandrup and E. H. Immergut, Editors,Chapter II/153). If r, is about equal to r₂, then the B₂ chain-end isincorporated into other chains throughout the reaction. If addition ofthe B₂ end-group by the propagating radical is not favored, then thechains are not incorporated into one another until late in thepolymerization or even not at all.

(d) Multi--Arm Polymers

An acrylic hyperbranched polymer of the type obtained byhomopolymerization of 2-(2-bromopropionoxy) ethyl acrylate, has nhalogen atoms per macromolecule, with n being equal to the number ofrepeat units. The halogen atoms are all alpha to a carbonyl group as aconsequence of either the propagation of a radical across the acrylicdouble bond followed by deactivation or from monomer ends which wereunchanged (the halogen atom was not homolytically abstracted, followedby propagation). As these halogen atoms are all alpha to a carbonylgroup, they are good initiating sites for ATRP. After purification, thehyperbranched polymer A was used as a macroinitiator for the ATRP ofbutyl acrylate.

(e) Comb Polymers

Copolymerization of 2-(2-bromopropionoxy) ethyl acrylate (2-BPEA) (0.5mol %) with butyl acrylate using a conventional radical initiator suchas 2,2'-azobisisobutyronitrile (AIBN), resulted in the synthesis of ahigh molecular weight, linear acrylic monomer (M_(n) =215,000; M_(w)/M_(n) =1.6). The copolymers have pendent bromine functional groups, anestimated average of 8 per chain, which are capable of initiating apolymerization under ATRP conditions. Use of the linear butylacrylate/2-BPEA copolymer as a macroinitiator for the ATRP of styrene(or methyl methacrylate) led to the formation of comb polymers, Scheme7. These comb polymers have a poly(butyl acrylate) backbone andpoly(styrene) (or poly(methyl methacrylate)) grafts. The resultingpolymers are good elastomeric materials. ##STR8##

TYPICAL POLYMERIZATION PROCEDURE

Purification of Reagents: The monomers used in the following exampleswere passed through aluminum trioxide to remove any inhibitors. Thesolvents and monomers were degassed by bubbling with argon.α,α'-Dibromo-p-xylene and 2,2'-bipyridine were recrystallized frombenzene and hexane, respectively. Copper bromide and copper chloridewere purified by stirring in glacial acetic acid, washed with ethanoland then dried.

Reaction Control: Monomer conversion was determined using a SHIMADZUGC-14A chromatograph with a DB-WAX, 30m column; with THF as an internalstandard. Gel permeation chromatography (GPC) measurements were carriedout using Phenogel columns (100 Å, 1000 Å, linear, guard) in series witha 410 differential refractometer, using DMF (acrylonitrile, 50° C.) orTHF (35° C.) as an eluent. The number average molecular weight was alsoobtained by ¹ H-NMR, using a 300 MHz BRUKER NMR spectrometer. Themolecular weight was also determined by Matrix Assisted Laser DesorptionIonization-Time of Flight (MALDI-TOF).

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

EXAMPLES Example 1

Polymerization of acrylonitrile with α,α'-dibromo-o-xylene/CuBr/dNbipyin various solvents

0.2003 g (7.595×10⁻⁴ mol) of α,α'-dibromo-p-xylene, 0.2174 g (1.519×10⁻³mol, of CuBr, and 0.7112 g (4.557×10⁻³ mol) of 2,2'-bipyridine (1/2/6mol ratio) were added to a SCHENLK flask. The reaction flask was tightlysealed with a rubber septum, degassed under vacuum, and charged withargon. 10 mL of solvent and 10 mL (0.1519 mol) of acrylonitrile werethen introduced via syringe. The reactions were carried out indiphenylether, dimethylformamide, propylene carbonate, and ethylenecarbonate as reaction solvents. The reaction mixture was immersed in anoil bath heated at 45° C., 55° C. or 100° C. Samples for kineticmeasurements were taken after a specific reaction time from the reactionmixture and diluted with THF. After kinetic measurement, polymers fromkinetic samples were precipitated by pouring into methanol then dried.These polymers were used for GPC measurement. The results ofpolymerizations were described in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Polymerization of acrylonitrile using α,α'-dibromo-o-xylene/Cu    Br/2,2'-                                                                      bipyridine as an initiating system in several solvents.                       Entry        Temp.        Conv.                                                                              M.sub.n                                        No. Solvent  (°C.)                                                                       M!/ I!                                                                            Time/h                                                                            (%)  (GPC)                                                                             M.sub.w /M.sub.n                           __________________________________________________________________________    1.sup.a                                                                           diphenylether                                                                          100 380  24  26   22000                                                                             1.32                                       2.sup.a                                                                           dimethylformamide                                                                      100 380  24  5    --  --                                         3.sup.a                                                                           propylene carbonate                                                                    100 380  24  81   17200                                                                             1.74                                       4.sup.b                                                                           "        100 380  24  69   13900                                                                             2.18                                       5.sup.a                                                                           ethylene carbonate                                                                     100 380  7   71   53100                                                                             1.71                                       6.sup.c                                                                           "        55  200  8   87   40400                                                                             1.54                                       7.sup.a                                                                           "        45  380  9   71   45100                                                                             1.34                                       8.sup.d                                                                           "        100 380  23  69   61900                                                                             1.83                                       __________________________________________________________________________     * I!/CuBr/2,2Bipyridine: a(=1/2/6), b(=1/2/4), c(=1/2/6), d(=1/3/6)  I!       represents the initiator.                                                

Example 2

Polymerization of acrylonitrile with 2-chloropropionitrile/CuBr/dNbipyin ethylene carbonate

0.114 g (7.995×10⁻⁴ mol) of CuBr and 0.3746 g (2.398×10⁻³ mol) of2,2'-bipyridine, and 25 g of ethylene carbonate were added to a schenlkflask. The reaction flask was tightly sealed with a rubber septum,degassed under vacuum, and charged with argon. 10 mL (0.1519 mol) ofacrylonitrile and 0.1415 mL (1.599×10⁻³ mol) of 2-chloropropionitrilewere then introduced via syringe. The reaction mixture was immersed inan oil bath heated at 47° C. or 64° C. Samples for kinetic measurementswere taken after a specific reaction time from the reaction mixture anddiluted with THF. After kinetic measurement, polymers from kineticsamples were precipitated by pouring into methanol, then dried. Thesepolymers were used for GPC measurement. The polymerization ofacrylonitrile using 2-chloropropionitrile/CuBr/2,2'-bipyridine (=1/2/6mol ratio) was also carried out in the same procedure.

The results of the polymerizations are described in Table

                                      TABLE 2                                     __________________________________________________________________________    Polymerization of acrylonitrile using 2-chloropropionitrile/CuBr/2,2'-        bipyridine as an initiating system in ethylene carbonate.                     entry                                                                             I!/CuBr/2,2'-                                                                           temp.                                                                            time                                                                             conv.                                                                            M.sub.n                                                                           M.sub.n                                                                           M.sub.n                                        no.                                                                              bipyridine                                                                            M!/ I!                                                                           (°C.)                                                                     (h)                                                                              (%)                                                                              (GPC)                                                                             (NMR)                                                                             (calc.)                                                                           M.sub.w /M.sub.n                           __________________________________________________________________________     9 1/0.5/1.5                                                                            95  47 48 86 25600                                                                             --  4300                                                                              1.16                                       10 1/0.5/1.5                                                                            95  64 48 93 29500                                                                             6700                                                                              4700                                                                              1.11                                       11 1/2/6  95  47 24 36 --  --  --  --                                         __________________________________________________________________________      I! represents the initiator                                             

Example 3

Polymerization of acrylonitrile with 2-bromopropionitrile/CuBr/dNbipy inethylene carbonate

The polymerizations using acrylonitrile/2-brompropionitrile (=95 and 190mol ratio) and 2-bromopropionitrile/CuBr/2,2'-bipyridine(=1/1/3,1/0.5/1.5, and 2/0.1/0.3 mol ratio) were carried out in ethylenecarbonate in similar procedure to example 2. The polydispersities andthe molecular weights of polymers at several reaction times weredescribed in Table 3.

                                      TABLE 3                                     __________________________________________________________________________    Polymerization of acrylonitrile using 2-bromopropionitrile/CuBr/2,2'-         bipyridine as an initiating system in ethylene carbonate at 64°        C.                                                                            entry                                                                             I!/CuBr/2.2'-                                                                           temp.                                                                            time                                                                             conv.                                                                            M.sub.n                                                                           M.sub.n                                                                           M.sub.n                                        no.                                                                              bipyridine                                                                            M!/ I!                                                                           (°C.)                                                                     (h)                                                                              (%)                                                                              (GPC)                                                                             (NMR)                                                                             (calc.)                                                                           M.sub.w /M.sub.n                           __________________________________________________________________________                     5  73 32800                                                                             5580                                                                              3680                                                                              1.23                                       12 1/1/3  95  44 10 84 35300                                                                             6060                                                                              4230                                                                              1.24                                                        23 91 37300                                                                             6450                                                                              4590                                                                              1.34                                                        5  81 28400                                                                             5590                                                                              4060                                                                              1.07                                       13 1/0.5/1.5                                                                            95  44 10 89 29600                                                                             5910                                                                              4460                                                                              1.11                                                        23 94 31900                                                                             6200                                                                              4750                                                                              1.12                                                        5  31 11600                                                                             2200                                                                              1550                                                                              1.05                                       14 1/0.1/0.3                                                                            95  44 10 32 13300                                                                             2610                                                                              1590                                                                              1.04                                                        23 38 15600                                                                             3030                                                                              1930                                                                              1.04                                                        5  91 28400                                                                             5820                                                                              4570                                                                              1.11                                       15 1/0.5/1.5                                                                            95  64 10 95 30400                                                                             6120                                                                              4760                                                                              1.12                                                        23 97 34200                                                                             6510                                                                              4870                                                                              1.10                                                        5  23 13600                                                                             2560                                                                              1130                                                                              1.04                                       16 1/0.1/0.3                                                                            95  64 10 32 15600                                                                             3080                                                                              1630                                                                              1.04                                                        23 49 18100                                                                             3900                                                                              2460                                                                              1.04                                                        5  77 47000                                                                             --  7710                                                                              1.09                                       17 1/0.5/1.5                                                                            190 64 9  81 47100                                                                             --  8140                                                                              1.14                                                        23 88 54100                                                                             --  8870                                                                              1.12                                                        5  26 20200                                                                             --  2640                                                                              1.05                                       18 1/0.1/0.3                                                                            190 64 9  33 25200                                                                             --  3310                                                                              1.04                                                        23 48 31600                                                                             --  4860                                                                              1.05                                       __________________________________________________________________________      I! represents the initiator                                             

Example 4

Polymerization of acrylonitrile with 2-chloropropionitrile/CuBr/dNbipyin ethylene carbonate

The polymerizations using(acrylonitrile)/(2-chloropropionitrile)/CuBr/2,2'-bipyridine(=1/0.5/1.5mol ratio) were carried out in ethylene carbonate at 64° C. in similarprocedure to example 2. The polydispersities and the molecular weightsof polymers at several reaction times are described in Table 4.

                                      TABLE 4                                     __________________________________________________________________________    Polymerization of acrylonitrile using 2-chloropropionitrile/CuCl/2,2'-        bipyridine as an initiating system in ethylene carbonate at 64°        C.                                                                                 I!.CuBr/2,                                                               entry                                                                             2'-        time                                                                             conv.                                                                             M.sub.n                                                                           M.sub.n                                                                            M.sub.n                                        no. bipyridine                                                                           M!/ I!                                                                            (h)                                                                              (%) (GPC)                                                                             (NMR)                                                                              (calc.)                                                                           M.sub.w /M.sub.n                           __________________________________________________________________________                   5  71  --  3110 3550                                                                              1.21                                       19  1/0.5/1.5                                                                           95   9  89  --  3610 4460                                                                              1.21                                                      24 94  --  4670 4720                                                                              1.21                                       __________________________________________________________________________      I! represents the initiator                                             

Example 5

Preparation of A-B-A block copolymer

Macroinitiators having a poly(styrene) backbone and a halogen chain-endfunctionality were prepared by "living" cationic polymerization ofstyrene with 1-PhEtCl/SnCl₄ initiating system in the presence of n-Bu₄NCl at -15° C. in methylene chloride in a schenlk flask under drynitrogen. The results are summarized in Table 5. After 30 minutes, thepolymerization was terminated by adding prechilled methanol. Thepolymers were purified by repeated dissolution-precipitation indichloromethane/methanol, and dried under vacuum. The macroinitiatorsthus synthesized have a narrow polydispersity index (M_(w) /M_(n)=1.17); end group analysis by ¹ H-NMR showed that polystyrene containthe CH₂ CH(Ph)--Cl terminal group (broad signal at about 4.4 ppm). Thepolystyrene macroinitiator having halogen chain-end functionality wasused as a macroinitiator in an atom transfer radical polymerizationusing styrene, methyl acrylate or methyl methacrylate as monomers. Table5 summarizes representative polymerization results for cationicpolymerization of styrene (exp. 1), and a homogeneous ATRP of styrene(St) (exp. 2), methyl acrylate (MA) (exp. 3) and methyl methacrylate(MMA) (exp. 4), initiated with the macroinitiator poly(styrene)-Cl(PSt-Cl) and catalyzed byCuCl/4,4'-(1-butylpentyl)-2,2'-bipyridine(dNbipy).

                                      TABLE 5                                     __________________________________________________________________________    Results obtained by transformation of "living" cationic to "living"           radical                                                                       polymerization                                                                Exp                                                                              Monomer   Initiating system                                                                        Temp °C.                                                                    M.sub.n,th                                                                        M.sub.n,exp                                                                       M.sub.w /M.sub.n                         __________________________________________________________________________    1  CH.sub.2 ═CH(Ph)                                                                    1-PhEtClSnCl.sub.4 /nBu.sub.4 NCl                                                        -15  2080                                                                              2100                                                                              1.17                                     2  CH.sub.2 ═CH(Ph)                                                                    PSt-Cl/CuCl/dNbipy                                                                       100  5100                                                                              5080                                                                              1.10                                     3  CH.sub.2 ═CH(COMe)                                                                  PSt-Cl/CuCl/dNbipy                                                                       100  6200                                                                              6330                                                                              1.20                                     4  CH.sub.2 ═CCH.sub.3 (COMe)                                                          PSt-Cl/CuCl/dNbipy                                                                       100  10100                                                                             11090                                                                             1.57                                     __________________________________________________________________________     Conditions: Exp. 1  St!.sub.o = 1 mol/L,  1PhEtCl!.sub.o = 5 ×          10.sup.-2 mol/L,  1PhEtCl!.sub.o / SnCl.sub.4 !.sub.o / nBu.sub.4             NCl!.sub.o = 1/5/2, CH.sub.2 Cl.sub.2 solvent, conversion = 98%, Exp. 2        St!.sub.o = 3 mol/L,  PStCl!.sub.o = 0.1 mol/L,  PStCl!.sub.o                / CuCl!.sub.o / dNbipy!.sub.o = 1/1/2, C.sub.6 H.sub.5 CH.sub.3 solvent,      conversion = 98.5%; Exp. 3  MA!.sub.o = 4.76 mol/L,  PStCl!.sub.o = 0.1       mol/L,  PStCl!.sub.o / CuCl!.sub.o / dNbipy!.sub.o = 1/1/2, C.sub.6           H.sub.5 CH.sub.3 solvent, conversion = 99.5%; Exp. 4  St!.sub.o = 8 mol/L      PStCl!.sub.o = 0.1 mol/L,  PStCl!.sub.o / CuCl!.sub.o / dNbipy!.sub.o =      1/1/2, C.sub.6 H.sub.5 CH.sub.3 solvent, conversion = 97.5%.             

The experimental values for the number average molecular weight(M_(n),Exp.) agree with the theoretical value of M_(n) (M_(n),th) whichwere calculated using expression (1):

    M.sub.n,th=(Δ M!.sub.0 / initiator!.sub.0)×(M.sub.w).sub.0 ×conversion                                         (1)

where (M_(w))₀ is the formula weight of the monomer, which assumes thateach polymer contains one halogen chain- end group. The GPCchromatograms of starting PSt-Cl and PSt-b-PSt-Cl, PSt-b-PMA-Cl andPSt-b-PMMA-Cl copolymers are illustrated in FIGS. 5-7. The reactionmixture of the block copolymer synthesis was diluted with THF andinjected directly into the GPC in order to avoid any fractionation ofthe polymer sample during isolation. The GPC measurements showed thatthe molecular weight distribution of the block copolymers weresubstantially unimodal and narrow. No signal attributed to startingmacroinitiator was detected.

The structure of the block copolymers was analyzed by ¹ H-NMRspectroscopy. FIGS. 8 and 9 illustrate 300 MHz , ¹ H-NMR spectra ofPSt-b-PMA-Cl and PSt-b-PMMA-Cl copolymers. The number average molecularweight (M_(n)) determined by NMR spectra, by integration of the aromaticprotons of the macroinitiator and methoxy group from PMA and PMMA,agrees very well with those determined by GPC. The tacticity of PMMAbased on CH₃ signals was (rr)=59%, (rm)=32% and (mm)=9%.

In a schenlk flask under nitrogen, the "living" PSt-Cl macroinitiatorobtained by cationic polymerization was deactivated by adding methylacrylate at -15° C. After raising the temperature, to room temperature,CH₂ Cl₂, Lewis acid and ester were removed under vacuum. A solution ofCuCl-dNbipy in toluene was added to the PSt-Cl product, followed by therequired amount of methyl acrylate and the temperature was increased to100° C. Experimental conditions identical to those summarized in Table 5(exp. 3) were used. The GPC traces of macroinitiator and copolymerPSt-b-PMA-Cl confirm the successful one pot transformation as shown inFIG. 10.

Example 6

Synthesis of hyperbranched Polystyrene

The homopolymerization of chloromethyl styrene (CMS) was carried out inbulk with 1 mole % CuCl, and 3 mole % 2,2'-bipyridyl. After 6 hours at110° C. the conversion, determined by ¹ H-NMR, was 64%. The reactionmixture was precipitated into methanol/brine for purification. SEC wasperformed on the polymer sample and the molecular weight was found tobe: M_(n) =1490, M_(w) /M_(n) =1.4. The molecular weight as determinedby ¹ H-NMR was found to be M_(n) =1760, which corresponds to a degree ofpolymerization (DP) equal to 11.6.

Example 7

Synthesis of star copolymer

This synthesis was demonstrated by dissolving the hyperbranchedpolystyrene (DP=11.6) prepared in Example 6, in butyl acrylate (BA),along with CuCl and dNbipy, then heating to 120° C. After three hours,the conversion of the BA was 98% with M_(n) =153,400; M_(w) /M_(n) =2.6.It should be noted that this molecular weight is a low estimate of theactual molecular weight of the polymer due to the star-like nature ofthe polymer. The hydrodynamic volume of star, or branched, polymers issmaller than that of linear polymers with a similar molecular weight.This difference results in the star polymer having longer retentiontimes in a size exclusion chromatography (SEC) column, thereby giving anapparent, lower molecular weight.

By assuming that a butyl acrylate chain is grown from each function siteon the hyperbranched styrene, one can estimate the size of the butylacrylate chainsby dividing M_(n) (153,400) by the average number offunctional groups (11.6). The obtained result was a minimum average ofM_(n) =13,200 per arm.

Example 8

Synthesis of 2-(2-bromopropionoxy) ethyl acrylate (2-BPEA)

2-BPEA: Under argon, a solution of 2-bromopropionyl bromide (36.45 ml,348 mmol) in 50 ml of CH₂ Cl₂, was added drop-wise to a stirringsolution of 2-hydroxyethyl acrylate (40.0 ml, 348 mmol) and pyridine(31.0 ml, 383 mmol) in 250 ml of CH₂ Cl₂. The reaction was cooled in anice bath. During the addition, a white precipitate formed(pyridine-HBr). After complete addition of the acid bromide (one hour),the reaction was stirred at room temperature for three hours. Thisprecipitate was then filtered and the CH₂ Cl₂ evaporated. Additionalprecipitate and a yellow oil were obtained. The precipitate was filteredand washed with CH₂ Cl₂. The oil and CH₂ Cl₂ wash were combined andwashed with water (50 ml three times), then dried over MgSO₄ and treatedwith decolorizing carbon. The CH₂ Cl₂ was evaporated to give a yellowoil. Distillation of the oil at 80° C./10⁻⁷ mmHg gave a colorless oil.Yield 39.5 g (45%). 300 MHz ¹ H NMR (CDCl₃) δ: 6.43 (d, 1H); 6.14 (dd,1H); 5.89 (d, 1H); 4,39 (m, 5 H); 1.82 (d, 3H).

Example 9

Homopolymerization of 2-(2-bromopropionoxy) ethyl acrylate (2-BPEA):

To a 10 ml round bottom flask, copper (I) bromide (43.6 mg, 0.3 mmol),copper(II) bromide (6.7 mg, 0.03 mmol), 4,4'-di-t-butyl-2,2'-dipyridyl(272.4 mg, 0.99 mmol) and a magnetic stirring bar were added. The flaskwas sealed with a rubber septum. The contents of the flask were thenplaced under vacuum and back-filled with argon (three times). Distilledand degassed 2-BPEA (5.0 ml, 30.9 mmol) was then added via a syringe.The flask was heated in an oil bath at 100° C., and stirred for 3.5hours. Conversion was determined by ¹ H NMR (88.6%). The reactionmixture was dissolved in THF and precipitated into methanol/brine (threetimes). The polymer was obtained as a viscous solid and was dried undervacuum at room temperature for two days. The results are presented inTable 10 below:

Example 10

Multi-arm Star Poly(butyl acrylate):

Homopolymer of 2-BPEA (DP=78) (1.0 g, 0.51 mmol (4 mmol Br)), copper-(I)bromide (29.1 mg, 0.2 mmol), 4,4'-di(1-butylpentyl)-2,2'-dipyridyl(163.2 mg, 0.4 mmol), and a magnetic stirring bar were added to a 50 mlround bottom flask. The flask was sealed with a rubber septum. Thecontents of the flask were placed under vacuum and back-filled withargon (three times). Distilled and degassed butyl acrylate (30.0 ml,209.3 mmol) was added via a syringe. The contents of the flask weredissolved by stirring at room temperature. The flask was placed in anoil bath at 110° C., and stirred for 17 hours. Conversion was determinedby ¹ H NMR (79%). The reaction mixture was dissolved in THF andprecipitated into methanol/brine (three times). The polymer was obtainedas a viscous fluid and was dried under vacuum at room temperature fortwo days. M_(n) =111,000 and M_(w) /M_(n) =2.6 for multi arm butylacrylate star polymer.

Example 11

Butyl Acrylate/2-BPEA Random Copolymer

To a 250 ml round bottom flask with a magnetic stirring bar, butylacrylate (30.0 ml, 209 mmol), 2-BPEA (170 uL, 1.05 mmol), AIBN (34.3 mg,0.209 mmol) and benzene 100.0 ml) were added. The flask was sealed witha rubber septum and the flask placed in a 60° C. oil bath. After 3 hoursthe reaction mixture became viscous; at which point it was quenched byprecipitation into methanol/brine (three times). The resulting polymerwas dried under vacuum at room temperature for one day. Yield 75%, M_(n)=215,000; M_(w) /M_(n) =1.6.

Example 12

Poly(Butyl Acrylate-g-Methyl Methacrylate):

5 g of poly(butyl acrylate-co-2-BPEA) was dissolved in 15.0 g ofdimethoxybenzene (DMB) at 85° C. in a stoppered round bottom flask.Separately, in a 5 ml round bottom flask, copper(I) bromide (12.3 mg,0.085 mmol), copper(II) bromide (1.8 mg, 0.008 mmol), and4,4'-di(1-butylpentyl)-2,2'-dipyridyl (75.7 mg, 0.19 mmol) weredissolved in methyl methacrylate (MMA) (3.0 ml, 28 mmol) under oxygenfree conditions. 1.8 ml of this MMA solution was then added to a DMBsolution at 85° C. The reaction was heated for 18 hours at 85° C. whilestirring. The reaction mixture was dissolved in THF and precipitatedinto methanol (two times). The white, tacky solid was dried under vacuumat room temperature. The results are presented in Table 11 below.

                                      TABLE 10                                    __________________________________________________________________________    Results of the Homopolymerization of 2-BPEA by                                Atom Transfer Radical Polymerization                                          Sample                                                                             Time (h)                                                                           Conv. (%).sup.m                                                                     M.sub.n.sup.b                                                                     M.sub.w /M.sub.n.sup.b                                                            M.sub.n.sup.c                                                                      DP.sup.c                                                                         DB.sup.d                                                                          DB.sup.e                                  __________________________________________________________________________    A    3.5  89    4,600                                                                             2.8 19,570                                                                              78                                                                              44.5                                                                              42.3                                      B    23.0 95    8,300                                                                             2.0 25,380                                                                             101                                                                              47.5                                                                              43.8                                      __________________________________________________________________________     .sup.a) As determined by 300 MHz .sup.1 H NMR.                                .sup.b) As determined by GPC versus narrow, linear poly(MMA) standards.       .sup.c) Degree of polymerization; as determined by 620 MHz .sup.1 H NMR.      .sup.d) Degree of branching as predicted by α = conversion/2.           .sup.e) Degree of branching: as determined by 620 MHZ .sup.1 H NMR.      

                  TABLE 11                                                        ______________________________________                                        Graft Copolymers of Butyl Acrylate                                            Monomer M.sub.n  M.sub.w /M.sub.n                                                                       Amt of Graft Copolymer (mol %)                      ______________________________________                                        Styrene 473,000  1.6      31%                                                 MMA     337,000  2.2      11%                                                 ______________________________________                                    

Example 13

Hyperbranched Acrylic Polymers with Narrow Polydispersity

Under oxygen free conditions (argon), methyl-α-chloroacrylate (1.0 g,6.6 mmol) was added to a tube containing benzyl chloride (5.75 mL, 0.05mmol), Cu(I)Cl (4.95 mg, 0.05 mmol), and4,4'-di-(1-butylpentyl)-2,2'-dipyridyl (40.8 mg, 0.10 mmol). Thereaction tube was sealed and then heated to 110° C. After 3 hours thegreen reaction mixture was viscous and was dissolved in THF. Thissolution was then precipitated into MeOH/brine (3 times).

                  TABLE 9                                                         ______________________________________                                        Sample   M!/ I!  Time (h) Conversion                                                                            M.sub.n                                                                             M.sub.w /M.sub.n                      ______________________________________                                        S-12-25 132      3.0      58      2190  1.15                                  S-12-39A                                                                              20       1.5      93      2260  1.24                                  S-12-41 66       4.5      90      1850  1.13                                  S-12-43 271      9.0      95      1950  1.15                                  ______________________________________                                    

Example 14

Polymerization of styrene initiated by difunctional polysiloxanemacroinitiator

Polymerization of styrene initiated by the difunctional polysiloxanemacroinitiator was carried out with CuCl/dNbipy catalyst in phenyl etherat 130° C. The macroinitiator dissolved well in the solvent and theproduced polymer did not precipitate, although the catalyst system wasnot homogeneous. The polymerization was stopped after 480 min, becausethe reaction mixture became very viscous. The final conversion ofstyrene monomer was 70%.

GPC traces of the difunctional polysiloxane macroinitiator and thesample at 480 min are shown in FIG. 12. The peak of produced polymer wasalways monomodal during the reaction, and shifted to higher molecularweight. The macroinitiator has M_(n) =9800, M_(w) /M_(n) =2.40, and thepolymer produced after 480 min has, after reprecipitation in MeOH, M_(n)=28300, and M_(w) /M_(n) =1.52.

The plot of M_(n) and polydispersity dependence on conversion in thispolymerization is shown in FIG. 13. A linear increase of number averagemolecular weight, M_(n), versus monomer conversions was observed. Thepolydispersity decreased with the progress of polymerization. It showsthe reaction was well controlled and the polystyrene blocks have lowpolydispersity.

¹ H-NMR spectrum of the final product ofpoly(styrene-b-dimethylsiloxane-b-styrene) copolymer is shown in FIG.14. It reveals that the polymer consists of polystyrene andpolydimethylsiloxane. The molar ratio of styrene to dimethylsiloxaneunit was 0.84.

Example 15

Polymerization of butyl acrylate initiated by difunctional polysiloxanemacroinitiator

Similarly to the poly(styrene-b-dimethylsiloxane-b-styrene) triblockcopolymers, the poly(butyl acrylate-b-dimethylsiloxane-b-butyl acrylate)triblock copolymer was prepared. The polymerization of butyl acrylateinitiated by the difunctional polydimethylsiloxane macroinitiator wascarried out with CuCl/dNbipy in 1,4-dimethoxybenzene at 100° C. Thepolymerization was stopped at 1020 min because of high viscosity. Theproduced polymer after 1020 min has M_(n) =24000, and M_(w) /M_(n)=1.58. The final product after reprecipitation from MeOH, was viscoussolid with M_(n) =36500, M_(w) /M_(n) =1.32.

Example 16

Hydrosilation of 2-(4'-chloromethyl-benzyl)ethyldimethyl-silane tovinyldimethylsilyl terminated high-molecular-weight polydimethylsiloxane

A mixture of vinyldimethylsilyl terminated polydimethylsiloxane(Mn=30,000-40,000; 10.00 g),2-(4'-chloromethylbenzyl)ethyldimethylsilane (0.20 g), Pt {(CH₂ =CH)Me₂Si}₂ O!₂ complex xylene solution (2.0×10⁻⁶ mmol) and benzene (5.0 ml)was stirred at 70° C. for 3 hours. Disappearance of the vinyl group ofthe polysiloxane was confirmed by ¹ H-NMR. The reaction mixture wasreprecipitated in MeOH to remove excess initiator.

Example 17

Polymerization of styrene initiated by high-molecular-weightpolysiloxane macroinitiator

The polymerization was carried out in a previously dried flask equippedwith a magnetic stirring bar under Ar. The preparedhigh-molecular-weight polysiloxane macroinitiator (2.0 g), CuCl (0.043g), dNbipy (0.36 g) and anisole (1.33 ml) were put into the flask, andthen the flask was degassed three times. Styrene (2.0 ml) wastransferred to the flask by means of rubber septum and syringe/capillarytechnique. The mixture was stirred at 130° C. under Ar. The conversionof the polymerization was determined by gas chromatography (GC)measurement of sampled reaction mixture. After 6 hours the heating wasstopped, when the conversion of styrene was 47%. The reaction mixturewas purified by means of short Al₂ O₃ column and reprecipitation intoMeOH from THF. the final polymer was analyzed by ¹ H-NMR to show thatthe poly(dimethylsiloxane) core block has M_(n) =40,000 and thepolystyrene side block has M_(n) =9,200. THF solution of the polymer wascasted on a glass and the solvent was evaporated slowly to give anelastomeric material.

Example 18

Synthesis of Polysulfone

Polysulfone was synthesized in the following manner: To a 3-neck 300 mlround bottom flask with a Dean-Stark condenser, thermometer, andmagnetic stir bar, bisphenol A (5.36 g, 23.5 mmol), 4,4'-difluorosulfone(5.00 g, 19.9 mmol), potassium carbonate (8.13 g, 58.8 mmol), N,N'-dimethylacetamide (60 ml) and toluene (40 ml) were added. TheDean-Stark apparatus was filled with 20 ml of toluene. The reaction washeated to 140° C. for 4 h to dehydrate the reaction. The temperature wasthen increased to 170° C. overnight. The reaction mixture was cooled tort and precipitated into MeOH/water (50:50). The resulting polymer wasdissolved in THF and reprecipitated into MeOH/brine (2 times). Mass 7.53g; Yield: 79%; M_(n) =4,300, M_(w) /M_(n) =1.3.

Example 19

Synthesis of bromopropionyl end capped polysulfone

5.0 g of polysulfone was dissolved in 50 ml of dry THF. To this stirringsolution, pyridine (0.5 ml, 5.88 mmol) and 2-bromopropionyl bromide(0.62 ml, 5.88 mmol) were added. A precipitate formed. After stirring atrt for 1 h, the solution was precipitated into a methanol/water (50:50)mixture. The polymer was reprecipitated three times with THF intoMeOH/brine. Mn=4,600; M_(w) /M_(n) =1.3.

Example 20

Synthesis of Poly(styrene-b-sulfone-styrene)

1.0 g of the bromopropionyl end capped polysulfone (0.25 mmol, 0.5 mmolof Br), copper (1) bromide (36.1 mg, 0.25 mmol), dNbipy (202.4 mg, 0.5mmol), and 1.0 of dimethoxybenzene were charged to a 10 ml round bottomflask with a magnetic stir bar. The flask was sealed with a rubberseptum and then degassed with argon (vacuum/backfill). Degassed anddeinhibited styrene (2.6 g, 25 mmol) was then added to the reactionflask. The reaction was heated to 110° C. for 6 hours. Conversion asdetermined by ¹ H NMR was 67%. The polymer was purified by precipitationfrom THF into methanol. Mass: 2.35 g, 66% yield, M_(n) by GPC was 9,100,M_(w) /M_(n) =1.1. M_(n) by ¹ H NMR was 10,700, with 62% styrene byweight.

Example 21

Synthesis of poly(butyl acrylate-b-sulfone-butylacrylate)

1.0 g of the bromopropionyl end capped polysulfone (0.25 mmol, 0.5 mmolof Br), copper (1) bromide (36.1 mg, 0.25 mmol), dNbipy (202.4 mg, 0.5mmol), and 1.0 g of dimethoxybenzene were charged to a 10 ml roundbottom flask with a magnetic stir bar. The flask was sealed with arubber septum and then degassed with argon (vacuum/backfill). Degassedand deinhibited butyl acrylate (3.2 g, 25 mmol) was then added to thereaction flask. The reaction was heated to 110° C. for 6 hours.Conversion as determined by ¹ H NMR was 95%. The polymer was purified byprecipitation from THF into methanol. Mass: 2.85 g, 68% yield, M_(n) byGPC was 13,800, M_(w) /M_(n) =1.2, M_(n) by ¹ H NMR was 15,300, with 74%styrene by weight.

Example 22

Synthesis of Polyester from Adipic Acid and 1,6-Hexanediol

To a three neck round bottom flask with a Dean-Stark trap, nitrogeninlet and a magnetic stir bar, 1,6-hexanediol (5.0 g, 42.3 mmol), adipicacid (4.81 g, 32.9 mmol), 2-bromopropionic acid (1.44 g, 9.4 mmol) andtoluene (100 ml) were added. The reaction was heated to refluxovernight. A sample was taken for GPC analysis, M_(n) =2,100, M_(w)/M_(n) =1.5.

To a flask, under an argon atmosphere, containing copper(I) bromide,(1.36.7 mg, 0.94 mmol) and dNbipy (767.0 mg, 1.88 mmol), 53.8 ml ofdeinhibited and degassed styrene was added. This mixture was stirreduntil all solids were dissolved and a dark red solution had formed. Thissolution was transferred to the polyester/toluene solution by cannulaunder argon. The reaction was stirred at 110° C. for 16 hours. Thereaction mixture was then cooled and precipitated into methanol/brine (3times). Mass: 64.0 g, Yield 86%. GPC: M_(n) =5,950, M_(w) /M_(n) =1.3. ¹H NMR showed 81% styrene by weight.

Example 23

Preparation of Macromonomer from Hydrosilyl TerminatedPoly(dimethylsiloxane)

To a mixture of difunctional hydrosilyl terminatedpoly(dimethylsiloxane) (20.00 g;), vinylbenzyl chloride (3.29 ml,2.31×10⁻² mol; m,p-mixture) and benzene was added Pt((CH₂ ═CH)Me₂ Si)₂O₂) xylene solution (0.32 ml, 3.08×10⁻⁵ mol) at room temperature underair. The mixture was stirred at 50° C. for 1 h. A part of the reactionmixture was analyzed by ¹ H-NMR showing no remaining hydrosilyl group.The product was isolated by reprecipitation in MeOH. The product hadM_(n) =4400 and M_(w) /M_(n) =1.25.

Example 24

Polymerization of Styrene with the Macroinitiator

A mixture of the poly(dimethylsiloxane) macroinitiator (2.00 g), styrene(6.00 ml, 5.24×10⁻² mol), CuCl (0.068 g, 6.90×10⁻⁴ mol) and dNbipy (0.56g, 1.38×10⁻³ mol) was stirred at 130° C. under Ar. The mixture wascooled down after 90 min, and diluted with THF. The solution was passedthrough a short Al₂ O₃ column and poured into MeOH to give whiteprecipitate. The precipitate was combined and dried in vacuo. Theproduct had M_(n) =11000, M_(w) /M_(n) =1.15. The GPC traces were alwaysmonomodal during the polymerization.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters: Patent ofthe United States is:
 1. A process for making a (co)polymer, comprisingthe steps of:(a) polymerizing an AB₂ monomer of formula (V): ##STR9## inthe presence of a catalyst system, comprising: (i) a transition metalcompound and(ii) a ligand able to coordinate with said transition metalcompound to thereby initiate polymerization of said monomer and form abranched polymer; wherein R¹ and R² are independently selected from thegroup consisting of H, halogen, CF₃, straight or branched C₁ -C₂₀ alkyl,α,β-unsaturated straight or branched C₂ -C₁₀ alkenyl or alkynyl,α,β-unsaturated straight or branched C₂ -C₆ alkenyl substituted with ahalogen, C₃ -C₈ cycloalkyl, hetercyclyl, C(═Y)R⁵, C(═Y)NR⁶ R⁷ andYC(═Y)R⁸, where Y may be NR⁸ or O, R⁵ is C₂ -C₂₀ -alkyl, C₂ -C₂₀ alkoxy,aryloxy or heterocyclyloxy, R⁶ and R⁷ are independently H or alkyl offrom 1 to 20 carbon atoms, or R⁶ and R⁷ may be joined together to form aC₂ -C₅ alkylene group, thus forming a 3- to 6-membered ring, and R⁸ isH, straight or branched C₁ -C₂₀ alkyl or aryl; and R³ is selected fromthe group consisting of H, halogen, C₁ -C₆ alkyl, COOR⁹, where R⁹ is H,an alkali metal, or a C₁ -C₆ alkyl group, or aryl; and R₂ ⁴ is anorganic spacer group and A is selected from the group consisting of R₂ ⁴'--X and X, where X is a halogen, and R₂ ⁴ ' is selected from the groupconsisting of straight or branched C₂ -C₂₀ alkyl, α,β-unsaturatedstraight or branched C₂ -C₁₀ alkenyl or alkynyl, α,β-unsaturatedstraight or branched C₂ -C₆ -alkenyl, C₃ -C₈ cycloalkyl, heterocyclyl,C(═Y)R⁵, C(═Y)NR⁶ R⁷ and YC(═Y)R⁸, C(═Y)--Y--R⁵ --C(═Y)--R⁸ where Y maybe NR⁸ or O, R⁵ is alkyl of from 1 to 20 carbon atoms, alkoxy of from 1to 20 carbon atoms, aryloxy or heterocyclyloxy, R⁶ and R⁷ areindependently H or alkyl of from 1 to 20 carbon atoms, or R⁶ and R⁷ maybe joined together to form an alkylene group of from 2 to 5 carbonatoms, thus forming a 3- to 6-membered ring, and R⁸ is H, straight orbranched C₁ -C₂₀ alkyl and aryl; and R¹ and R³ may be joined to form agroup of the formula (CH₂)_(n') or C(═O)--Y--C(═O), where n' is from 2to 6 and Y is as defined above.
 2. The process of claim 1, wherein saidAB₂ monomer is selected from the group consisting ofp-chloromethylstyrene, methyl-a-chloroacrylate 2-(2-bromopropionoxy)ethyl acrylate, p-chlorosulfonyl styrene, vinyl chloroacetate andchloroacrylonitrile.
 3. The process of claim 1, wherein said branchedpolymer is a hyperbranched polymer having one or more radicallytransferable atoms or groups and wherein said process furthercomprises:(b) polymerizing a vinyl monomer in the presence of a catalystsystem comprising:(i) said hyperbranched polymer having one or moreradically transferable atoms or groups, (ii) a transition metalcompound, and (iii) a ligand, able to coordinate with said transitionmetal compound and initiate polymerization of said vinyl monomer.
 4. Theprocess of claim 3, wherein said hyperbranched polymer having one ormore radically transferable atoms or groups is a multi-functionalinitiator and wherein the copolymer formed is a multi-armed starcopolymer.
 5. The process of claim 4, wherein said AB2 monomer ischloromethyl styrene, and said vinyl monomer is butyl acrylate.
 6. Amulti-armed star copolymer prepared by the process as claimed in claim5.
 7. The process of claim 3, wherein said AB2 monomer is2-(2-bromopropionoxy) ethyl acrylate and said vinyl monomer is butylacrylate.
 8. A multi-armed star copolymer prepared by the process asclaimed in claim 7.